Esters of antibiotic nodusmicin

ABSTRACT

Novel antibacterially-active esters of antibiotic nodusmicin. Activity is demonstrated against Staphylococcus aureus, Streptococcus pyogenes, and Sarcina lutea. Thus, these esters can be used in various known environments, using well-known procedures, to eradicate or control susceptible microbes.

This is a division of application Ser. No. 175,409, filed Aug. 6, 1980.

BACKGROUND OF THE INVENTION

Antibiotic nodusmicin (U-59,761) is producible in a fermentation undercontrolled conditions using a biologically pure culture of the microbeSaccharopolyspora hirsuta strain 367, NRRL 12045. This antibiotic isactive against various bacteria, including Mycobacterium avium, S.lutea, K. pneumoniae, B. fragilis, and C. perfringens.

Our work to derive the structural formula for nodusmicin also enabled usto determine the structure for antibiotic U-59,760. We have determinedthat U-59,760 is the 9-O-pyrrole-2-carbonyl ester of nodusmicin.

The physical and chemical characteristics of U-59,760 cannot bedistinguished from the antibiotic known as compound 47,444 which isdisclosed in U.S. Pat. No. 4,148,883. Compound 47,444 is identified inU.S. Pat. No. 4,148,883 by its physical and chemical characteristics, aswell as antimicrobial activity. The production of compound 47,444 inU.S. Pat. No. 4,148,883 is accomplished by an entirely differentmicrobe, a Nocardia, than the S. hirsuta which produce nodusmicin. Arecent publication of the Journal of the American Chemical Societydiscloses the structure of compound 47,444. See JACS, 102:12, June 4,1980, pp. 4203-4209.

BRIEF SUMMARY OF THE INVENTION

Selective esterification of nodusmicin gives novel antibacteriallyactive esters. Specifically, employing selective esterificationprocedures there are obtained 9-O-esters of nodusmicin which possesssignificant antibacterial activity. Other esters which are disclosed arethe 18-O- and 11-O-esters which, though possessing antibacterialactivity, are much less active than the 9-O-esters. Also formed are di-Oesters and tri-O esters. Antibiotic nodusmicin can be shown by formulaI, infra.

In a broad aspect, the subject invention concerns esters formed by thereaction of nodusmicin with a hydrocarbon carboxylic acid of from 1 to18 carbon atoms, inclusive; halo-, nitro-, hydroxy-, amino-, cyano-,thiocyano-, and loweralkoxy- substituted hydrocarbon carboxylic acid offrom 1 to 18 carbon atoms, inclusive; and loweralkoxycarbonyl.

The most preferred esters of the subject invention are those whereinnodusmicin is reacted with acids of the generic structure A shown inChart III.

Preferred esters of the subject invention are those wherein nodusmicinis reacted with acids of the generic structure B also shown in ChartIII.

DETAILED DESCRIPTION OF THE INVENTION

We have determined that antibiotic nodusmicin (I) has three hydroxylgroups which we have labelled the C-18, C-9, and C-11 hydroxyls. Ourwork shows that the reactivity of the hydroxyls of nodusmicin toesterification and silylation decreases in the order 18>9>11. Thus thehydroxyl at C-11 is much less reactive than the hydroxyl at C-18. Twoprocesses can be employed to prepare esters of nodusmicin. One processis a random esterification of nodusmicin which produces mixturescontaining some of the desired C-9 ester. This process is outlined inChart I.

The preferred process, outlined in Chart II has three steps: (1)blocking of the most active C-18 hydroxyl; (2) esterification of the C-9hydroxyl; and (3) removal of the blocking group. These steps are nowdiscussed in detail.

Step I. This step is the selective blocking of the most reactive C-18hydroxyl. A suitable blocking group used in this sequence must have thefollowing qualifications. It must react selectively in high yield withthe C-18 hydroxyl. The resulting derivative must be stable during theesterification of the C-9 hydroxyl, be stable to chromatography, andeasily cleaved leaving the C-9 ester intact.

A blocking group, as used herein, is one which will be removed prior tothe obtention of the end product. It should be understood that at timesa acyl group can function as a blocking group.

Exemplified herein is the use of the t-butyldimethyl silyl ether (BDM)at C-18. Other trisubstituted silyl ethers, for example, trimethylsilyl,triethylsilyl, methyl-di-isopropylsilyl or t-butyl-diphenylsilyl can beused. Other means to block the C-18 hydroxyl include substituted andunsubstituted tetrahydropyranyl ethers, β,β,β-trichloroethyl ether,β-methoxyethoxymethyl ether, carbonate esters, such as carbo-t-butoxy,carbobenzyloxy, substituted carbobenzoxyl and the like. When (1) istreated with t-butyldimethylsilyl chloride in an organic solvent in thepresence of a base, such as imidazole [E. J. Corey and A. Venrateswarlu,J. Amer. Chem. Soc., 94, 6190 (1972).], 18-O-ether (3) is formed in highyield. Isolation requires chromatography. In addition varying amounts of9,18-O-diether (4) can be isolated.

Step 2. Esterification of silyl ether (3) usually gives preferentiallyC-9 ester (5) with varying amounts of C-11 ester (6) and diester (7). Bylimiting the amount of esterifying reagents employed, or length ofreaction time, the formation of diester (7) can be suppressed, thoughsometimes this leads to lower yields of monoester and also greateramounts of unreacted ether (3). Two methods of esterification can beemployed. Where acid chlorides are available, the acid chloride-pyridineesterification procedure is used. Generally, silyl ether (3) is treatedwith 1-3 molar equivalents of acid, 1.1-3.3 molar equivalents ofdicyclohexylcarbodiimide and 0.1-0.3 moles of 4-dimethylaminopyridine[A. Hassner and V. Alexanian, Tet. Letters, 4475 (1978) and F. E.Ziegler and G. D. Berger, Sym. Comm., 9, 539 (1979)]. The esterifiedproducts are usually isolated as a glass and characterized by cmr andhigh resolution ms. Mass spectral data for the esters are given in TableI. Table II gives chemical shifts for the C-13 NMR spectra for severaltypical BDM esters. Included are data for 9-O, 11-O and 9,11-di-O estersof 18-O-BDM-nodusmicin.

Step 3. Blocking groups are removed from the silyl ethers by treatmentwith fluoride ion (Bu,NF) in tetrahydrofuran (THF) by the method ofCorey (loc cit), or with dilute acid, to afford the appropriate ester.Purification is achieved by chromatography over silica gel.

In vitro antibacterial testing data, as measured by standard dipped discagar diffusion assays and Minimum Inhibitory Concentration (MIC)determinations, are recorded in Table II.

The agar diffusion assay uses standard 12.7 mm paper discs. The disc isdipped in a 1 mg./ml. methanolic solution of the compound tested, driedand applied to seeded agar trays. Inhibition zones are read after 16hours of incubation.

MIC's are determined using the standard microplate broth-dilutionmethod.

The broth used is BHI broth (Difco).

Compounds active against S. aureus can be used to disinfect washed andstacked food utensils contaminated with this bacterium. Further, theantibacterially-active esters of nodusmicin can be used asbacteriostatic rinses for laundered clothes, and for impregnating papersand fabrics; and, they are also useful for suppressing the growth ofsensitive organisms in plate assays and microbiological media. Theseuses are well-known in the antibiotic art. Accordingly, bacteriologicaltechniques are readily available to persons skilled in this art topractice such uses.

Acids which can be used in the esterification of nodusmicin are asdisclosed above, and as shown in Chart III. In its broadest aspect,carboxylic acids suitable for esterification include (a) saturated orunsaturated, straight or branched chain aliphatic carboxylic acids, forexample, acetic, propionic, butyric, isobutyric, tert-butylacetic,valeric, isovaleric, caproic, caprylic, decanoic, dodecanoic, lauric,tridecanoic, myristic, pentadecanoic, palmitic, margaric, stearic,acrylic, crotonic, undecylenic, oleic, hexynoic, heptynoic, octynoicacids, and the like; (b) saturated or unsaturated, alicyclic carboxylicacids, for example, cyclobutanecarboxylic acid, cyclopentanecarboxylicacid, cyclopentenecarboxylic acid, methylcyclopentenecarboxylic acid,cyclohexanecarboxylic acid, dimethylcyclohexanecarboxylic acid,dipropylcyclohexanecarboxylic acid, and the like; (c) saturated orunsaturated, alicyclic aliphatic carboxylic acids, for example,cyclopentaneacetic acid, cyclopentanepropionic acid, cyclohexaneaceticacid, cyclohexanebutyric acid, methylcyclohexaneacetic acid, and thelike; (d) aromatic carboxylic acids, for example, benzoic acid, toluicacid, naphthoic acid, ethylbenzoic acid, isobutylbenzoic acid,methylbutylbenzoic acid, and the like; and (e) aromatic-aliphaticcarboxylic acids, for example, phenylacetic acid, phenylpropionic acid,phenylvaleric acid, cinnamic acid, phenylpropiolic acid andnaphthylacetic acid, and the like. Suitable halo-, nitro-, hydroxy-,amino-, cyano-, thiocyano-, and lower alkoxyhydrocarbon carboxylic acidsinclude hydrocarboncarboxylic acids as given above which are substitutedby one or more of halogen, nitro, hydroxy, amino, cyano, or thiocyano,or loweralkoxy, advantageously loweralkoxy of not more than six carbonatoms, for example, methoxy, ethoxy, propoxy, butoxy, amyloxy, hexyloxy,and isomeric forms thereof. Examples of such substituted hydrocarboncarboxylic acids are:

mono- di, and trichloroacetic acid;

α- and β-chloropropionic acid;

α- and γ-bromobutyric acid;

α- and δ-iodovaleric acid;

mevalonic acid;

2- and 4-chlorocyclohexanecarboxylic acid;

shikimic acid;

2-nitro-1-methyl-cyclobutanecarboxylic acid;

1,2,3,4,5,6-hexachlorocyclohexanecarboxylic acid;

3-bromo-2-methylcyclohexanecarboxylic acid;

4- and 5-bromo-2-methylcyclohexanecarboxylic acid;

5- and 6-bromo-2-methylcyclohexanecarboxylic acid;

2,3-dibromo-2-methylcyclohexanecarboxylic acid;

2,5-dibromo-2-methylcyclohexanecarboxylic acid;

4,5-dibromo-2-methylcyclohexanecarboxylic acid;

5,6-dibromo-2-methylcyclohexanecarboxylic acid;

3-bromo-3-methylcyclohexanecarboxylic acid;

6-bromo-3-methylcyclohexanecarboxylic acid;

1,6-dibromo-3-methylcyclohexanecarboxylic acid;

2-bromo-4-methylcyclohexanecarboxylic acid;

1,2-dibromo-4-methylcyclohexanecarboxylic acid;

3-bromo-2,2,3-trimethylcyclopentanecarboxylic acid;

1-bromo-3,5-dimethylcyclohexanecarboxylic acid;

homogentisic acid, o-, m-, and p-chlorobenzoic acid;

anisic acid;

salicylic acid;

p-hydroxybenzoic acid;

β-resorcylic acid;

gallic acid;

veratric acid;

trimethoxybenzoic acid;

trimethoxycinnamic acid;

4,4'-dichlorobenzilic acid;

o-, m-, and p-nitrobenzoic acid;

cyanoacetic acid;

3,4- and 3,5-dinitrobenzoic acid;

2,4,6-trinitrobenzoic acid;

thiocyanoacetic acid;

cyanopropionic acid;

lactic acid;

ethoxyformic acid (ethyl hydrogen carbonate); and the like.

Acids which can be used to make esters considered to be the mostpreferred are, for example,

pyrrole-3-carboxylic,

4-bromo-2-pyrrolecarboxylic,

5-bromo-2-pyrrolecarboxylic,

4-nitropyrrole-2-carboxylic,

4-aminopyrrole-2-carboxylic,

4-methoxy-2-pyrrolecarboxylic,

4-hydroxy-2-pyrrolecarboxylic,

5-hydroxy-2-pyrrolecarboxylic,

4-methylpyrrole-2-carboxylic,

2-methylpyrrole-3-carboxylic,

thiophene-2-carboxylic,

thiophene-3-carboxylic,

3-chloro-thiophene-2-carboxylic,

5-nitro-thiophene-2-carboxylic,

amino thiophene-2-carboxylic,

3-methoxythiophene-2-carboxylic,

3-bromothiophene-2-carboxylic,

3-methylthiophene-2-carboxylic,

2-acetylaminothiophene-3-carboxylic,

3-methylthiophene-2-carboxylic,

2-methylthiophene-3-carboxylic,

4-bromomethylthiophene-3-carboxylic,

4-methoxymethylthiophene-3-carboxylic,

4-methylthioethylthiophene-3-carboxylic,

furoic,

3-furoic,

4-bromofuroic,

5-nitrofuroic,

5-aminofuroic,

4-methoxy-5-methyl-2-furoic,

4-hydroxyfuroic,

5-methylthiofuroic,

5-ethylfuroic, and the like.

Acids which can be used to make esters considered to be preferred are,for example,

imidazole-2-carboxylic,

4-imidazolecarboxylic,

5-methyl-2-imidazolecarboxylic,

4-(or 5)-amino-5-(or 4)-imidazolecarboxylic,

histidine,

pyrazole-3-carboxylic,

pyrazole-4-carboxylic,

4-bromopyrazole-3-carboxylic,

3-methylpyrazole-5-carboxylic,

2-thiazolecarboxylic,

4-thiazolecarboxylic,

5-thiazolecarboxylic,

iso-oxazole-3-carboxylic,

isooxazole-5-carboxylic,

oxazole-4-carboxylic,

1,2,3-triazole-4-carboxylic, and the like.

The above acids are well-known and available to those skilled in theart.

Preparation of Antibiotic nodusmicin Part A. Fermentation

A biologically pure culture of Saccharopolyspora hirsuta strain 367,NRRL 12045, is used to inoculate 500-ml. Erlenmeyer seed flaskscontaining 100 ml. of sterile medium consisting of the followingingredients:

    ______________________________________                                        Glucose monohydrate     25 g./l.                                              Pharmamedia*            25 g./l.                                              Tap water q.s.          1 liter                                               ______________________________________                                         *Pharmamedia is an industrial grade of cottonseed flour produced by           Traders Oil Mill Company, Fort Worth, Texas.                             

The seed medium presterilization pH is 7.2. The seed inoculum is grownfor three days at 28° C. on a Gump rotary shaker operating at 250 rpmand having a 21/2 inch stroke.

After three days incubation, the seed medium is used to inoculate (theinoculation rate is 5 ml. of seed inoculum per 100 ml. of fermentationmedium) a series of 500-ml. Erlenmeyer flasks containing sterilefermentation medium consisting of the following ingredients:

    ______________________________________                                        Glucose monohydrate    10 g./l.                                               Dextrin                20 g./l.                                               Corn steep liquor      2.5 g./l.                                              NH.sub.4 NO.sub.3      3.0 g./l.                                              NaCl                   2.0 g./l.                                              CaCO.sub.3             5.0 g./l.                                              pH-7.2 (presterilization)                                                     ______________________________________                                    

The fermentation flasks are incubated at a temperature of 28° C. on aGump rotary shaker operating at 250 rpm and having a 21/2 inch stroke.Harvest is usually after about 5 days of fermentation. A typical 5 dayfermentation has the following titers of antibiotic in the fermentationbroth:

    ______________________________________                                        Day        S. lutea Assay, Bu/ml.                                             ______________________________________                                        2           8.0                                                               3          10.4                                                               4          10.4                                                               5          11.2                                                               ______________________________________                                    

In the assay results, a biounit (BU) is defined as the concentration ofthe antibiotic which gives a 20 mm. zone of inhibition under thestandard assay condition. Thus, if, for example, a fermentation beer hasto be diluted 1/100 to give a 20 mm. zone of inhibition, the potency ofsuch beer is 100 Bu/ml.

B. Recovery and Purification

The whole beer (ca. 5,000 l.) from a fermentation, as described above,is adjusted to pH 7.3 with NaOH and filtered on a 30 inch filter pressusing diatomaceous earth as a filter aid. During the filtrationoperation wash water is applied to the filter cake. From the filtrationoperation is recovered 5,500 l. of clear fermentation broth which isthen extracted twice with methylene dichloride (1,400 l. each time) togive a total of 2.800 l. of solvent extract. This solvent extract isconcentrated in vacuo to 10 l. Assay on a standard S. lutea disc plateassay gives a value of 2,424 Bu/ml.

The extract concentrate described above (9 l.), is chromatographed overa column containing 9 kg. of silica gel (E. Merck-silica gel 7734). Thecolumn is eluted as follows:

20 liters methylene dichloride; then 40 liters 2% methanol in methylenedichloride; then 150 liters 5% methanol in methylene dichloride, then100 liters 10% methanol in methylene dichloride. Four liter fractionsare collected after an 80 liter forerun. Fractions 10-19 containantibiotic nodusmicin. Crystalline antibiotic nodusmicin (41.4 g.) isobtained on concentration of fractions 10-19. Another 12.8 g. ofcrystalline antibiotic nodusmicin is obtained by chromatography of themother liquors over silica gel with ethyl acetate as eluant.

The following examples are illustrative of the products and process ofthe invention, but are not to be construed as limiting. All percentagesare by weight and all solvent mixture proportions are by volume unlessotherwise noted.

EXAMPLE 1 Random Process of Ester Formation, Chart I 18-O- and9-O-Benzoate Esters of nodusmicin

Benzoyl chloride (560 mg., 4 mmoles) is added to 846 mg. (2 mmoles) ofnodusmicin dissolved in 10 ml. of ethyl acetate and 480 mg. (6 mmoles)of pyridine. After standing at ambient temperature overnight, thereaction mixture is diluted with water and methylene dichloride. Themethylene dichloride extract is washed successively with dilute acid andbase. Following drying and evaporation, a mixture of crude benzoates isobtained. This material is chromatographed over 35 g. of Silica Gel 60(EM Reagents) using Skellysolve B-ethyl acetate (4:1) for elution.Fractions are monitored by tlc (silica gel G; Skellysolve B-ethylacetate) (4:1); and combined on the basis of the tlc profile. Fractionsof 121 mg. (11.56% yield) of 18-O-benzoyl-nodusmicin and 92 mg. (8.7%)of 9-O-benzoyl-nodusmicin are obtained. Mol. wt. calculated for C₃₀ H₃₈O₈ : 526.2566. Found 18-O-benzoyl, 526.2591; 9-O-benzoyl, 526.2581. At aconcentration of 1 mg./ml. a 0.5 inch disc gave a zone of inhibition onan agar tray seeded with S. lutea as follows: 18-O-benzoyl ester, 24 mm;9-O-benzoyl ester, 30 mm.

EXAMPLE 2 Selective Process of Ester Formation, Chart II Blocking ofnodusmicin (Step 1) 18-O-t-Butyldimethylsilyl-nodusmicin (3) and18,9-O-Di-t-butyldimethylsilyl-nodusmicin (4)

A solution of 2.16 g. (5.12 mmol) of nodusmicin, 1.7 g. (25 mmol) ofimidazole and 1.5 g. (10 mmol) t-butyldimethylsilyl chloride in 25 ml.of dimethylformamide (DMF) is kept at ambient temperature for 18 hours.The solvent is distilled under vacuum. The residue is dissolved inmethylene dichloride and washed several times with water. The solutionis dried and concentrated. Chromatography over 105 g. of silica gelusing chloroform-ethyl acetate (2:1) for elution affords 645 mg. (19.4%)of diether (4) and 1.787 g. (65.1%) of 18-O-ether (3).

Observed exact mass of molecular ion for (4) is 650.4034 (calculated forC₃₅ H₆₂ O₇ Si₂, 650.4034); for (3) the observed is 536.3160 (calculatedfor C₂₉ H₄₈ SiO₇, 536.3169).

EXAMPLE 3 Esterification (Step 2) Acid-Carbodimide Procedure (PreferredProcess) 9-O-Thiophene-3-carbonyl (5) and9,11-O-Dithiophene-3-carbonyl-18-O-BDM-nodusmicin (7)

A mixture of 602 mg. (1.12 mmoles) of ether (3) from above, 272 mg.(2.13 mmoles) of thiophene-3-carboxylic acid, 482 mg. (2.3 mmoles) ofdicyclohexylcarbodiimide, and 25 mg. of 4-dimethylaminopyridine in 20ml. of THF is stirred at ambient temperature for 18 hours. Thedicyclohexylurea which precipitates is removed by filtration and thefiltrate evaporated. The residue is chromatographed over 35 g. of SilicaGel 60 using ethyl acetate-Skellysolve B (1:3) for elution. A fractionof 212 mg. (25.0% yield) of diester (7) is eluted first, followed by 357mg. (49.3%) of 9-O-ester (5).

The exact masses of these products are as follows: 9-O-ester (5): calcdfor C₃₄ H₅₀ O₈ SiS 646.2996; Found 646.2971. 9,11-O-Diester (7): calcdfor C₃₉ H₅₂ O₉ SiS₂ 756.2822; Found 756.2824.

EXAMPLE 4 Acid Chloride-Pyridine Procedure 9-O-2-Furoyl-11-O-2-Furoyl-,9,11-O-Difuroyl-18-O-BDM-nodusmicin

2-Furoyl chloride (2.02 mmoles, 270 mg.) is added to a cooled solutionof 750 mg. (1.4 mmole) of ether (3) in 7 ml. of pyridine. After 30minutes, 198 mg. additional furoyl chloride is added. The mixture isstirred for 30 minutes and diluted with methylene chloride. Theresulting solution is washed successively with dilute acid and base.After drying and concentrating, the residue is chromatographed over 35g. of silica gel. The column is eluted with Skellysolve B-ethyl acetate(4:1) to give: 9,11-O-diester, 129 mg. (14.1%); 9-O-ester, 325 mg.(40.9%) and 129 mg. of 11-O-ester (16.3%). The exact masses for thesecompounds are found in Table I.

EXAMPLE 5 Removal of Blocking Group (Step 3)9-O-Thiophene-3-carbonyl-nodusmicin

9-O-Thiophene-3-carbonyl-18-O-BDM-nodusmicin from above (357 mg.), isdissolved in 7.5 ml. of THF, and 2 ml. of tetrabutylammonium fluoride inTHF (0.5 M) is added. After 30 minutes the mixture is evaporated. Theresidue is partitioned between water-ether. The ether solution is driedand concentrated. The residue is chromatographed over 25 g. of methanol(30:1). The product fraction weighs 247 mg. (84%) and is identified as9-O-thiophene-3-carbonylnodusmicin. Exact mass; calcd for C₂₈ H₃₆ O₈ S,532.2131; Found 532.2127.

A solution of 1 mg./ml. when applied to a 0.5 inch disc and plated onagar trays seeded with the given organism, showed the following zones ofinhibition: S. lutea, 40 mm.; S. aureus, 35 mm.

EXAMPLE 6

Upon reacting an appropriate acid having the acyl moiety shown in TableI with the 18-O-t-butyldimethylsilyl ether of antibiotic nodusmicin,there is obtained the corresponding ester.

EXAMPLE 7

Upon removal of the blocking group from the 18-position of the compoundsin Example 6 with tetrabutylammonium fluoride, or a dilute mineral acid,for example, dilute HCl, there are obtained the compounds given in TableII. ##STR1## wherein X is selected from the group consisting of N, S,and O; R₁, R₂, and R₃ can be the same or different, and are selectedfrom the group consisting of H, OH, halogen, NO₂ , alkyl of 1-8 C,inclusive, NH₂, NR₄ R₅, wherein R₄ and R₅ can be selected from the groupconsisting of H, OH, and alkyl and substituted alkyl, wherein the alkylis from 1 to 8 carbon atoms, inclusive, and the substituent onsubstituted alkyl can be OH, halogen, SH, and the like; O alkyl, Salkyl, O acyl, and N acyl; excluding wherein X is N, R₁ =R₂ =R₃ are H,and COOH is on the two position of the molecule. ##STR2## wherein Y isselected from the group consisting of nitrogen, sulfur or oxygen; COOHcan be at any one of the unoccupied ring carbon atoms; and R₁ is asdefined above and can be on any one of the unoccupied ring carbon atoms.

                  TABLE I                                                         ______________________________________                                        Esters of 18-O--BDM-Ether of nodusmicin                                                                       Exact                                         Compound       Molecular Weight Mass                                          ______________________________________                                        9-O--Benzoyl-  C.sub.36 H.sub.52 O.sub.8 Si                                                              640.3431 640.3411                                  11-O--Benzoyl-                                                                9,11-O--Dibenzoyl-                                                            9-O--Nicotinoyl-                                                                             C.sub.35 H.sub.51 O.sub.8 NSi                                                             641.3384 641.3394                                  9-O-2-Furoyl-  C.sub.34 H.sub.50 O.sub.9 Si                                                              630.3224 630.3253                                  11-O-2-Furoyl-                      630.3209                                  9,11-O--Difuroyl-                                                                            C.sub.39 H.sub.52 O.sub.11 Si                                                             724.3279 724.3251                                  9-O--N--Cbz-L-prolyl-                                                                        C.sub.42 H.sub.61 O.sub.10 NSi                                 9-O--N--t-BOC--L-prolyl-                                                      9-O--Pyrrole-2-carbonyl-                                                                     C.sub.34 H.sub.51 O.sub.8 NSi                                                             629.3384 629.3370                                  9-O--Picolinoyl-                                                                             C.sub.35 H.sub.51 O.sub.8 NSi                                                             641.3384 641.3362                                  9-O--Thiophene-3-carbonyl-                                                                   C.sub.34 H.sub.50 O.sub.8 SiS                                                             646.2996 646.2971                                  9,11-O--Dithiophene-3-                                                                       C.sub.39 H.sub.52 O.sub.9 SiS.sub.2                                                       756.2822 756.2824                                  carbonyl                                                                      9-O--Isonicotinoyl-                                                                          C.sub.35 H.sub.51 O.sub.8 NSi                                                             641.3384 641.3362                                  9,11-Di-O--isonicotinoyl-                                                                    C.sub.41 H.sub.54 O.sub.9 N.sub.2 Si                                                      746.3598 746.3609                                  9-O--N--Methylpyrrole-2-                                                                     C.sub.35 H.sub.53 O.sub.8 NSi                                                             643.3540 643.3510                                  carbonyl-                                                                     9-O--5-Nitrofuroyl-                                                                          C.sub.39 H.sub.51 O.sub.11 NSi                                 9-O--Thiophene-2-carbonyl                                                                    C.sub.34 H.sub.50 O.sub.8 SiS                                                             646.2996 646.3022                                  9-O--Pyrazine-2-carbonyl                                                                     C.sub.34 H.sub.50 O.sub.8 N.sub.2 Si                                                      642.3336 642.3306                                  9,11-O--Dipyrazine-2-                                                                        C.sub.39 H.sub.52 O.sub.9 N.sub.4 Si                                                      748.3503 748.3527                                  carbonyl                                                                      9-O--5-Methylpyrrole-2-                                                                      C.sub.35 H.sub.53 O.sub.8 NSi                                                             643.3540 643.3555                                  carbonyl                                                                      9-O--Indole-2-carbonyl-                                                       9-O--5-Nitropyrrole-2-                                                                       C.sub.34 H.sub.50 O.sub.10 N.sub.2 Si                                                     674.3234 674.3216                                  carbonyl-                                                                     11-O--5-Nitropyrrole-2-                                                                      C.sub.34 H.sub.50 O.sub.10 N.sub.2 Si                                                     674.3234 674.3234                                  carbonyl-                                                                     9-O--4-Nitropyrrole-2-                                                                       C.sub.34 H.sub.50 O.sub.10 N.sub.2 Si                                                     674.3234 674.3209                                  carbonyl-                                                                     9-O--3-Furoyle C.sub.34 H.sub.50 O.sub.9 Si                                                              630.3224 630.3260                                  9,11-O--Di-3-furoyl-                                                                         C.sub.39 H.sub.52 O.sub.11 Si                                                             724.3279 724.3236                                  9-O--5-Bromofuroyl-                                                                          C.sub.34 H.sub.49 O.sub.9 BrSi                                                            708.2330 708.2349                                  9,11-O--Di-5-bromofuroyl-                                                                    C.sub.39 H.sub.50 O.sub.11 Br.sub.2 Si                                                    880.1490 880.1503                                  ______________________________________                                         Cbz = carbobenzoxy                                                            tBOC = tertiary butoxycarbonyl                                           

                                      TABLE II                                    __________________________________________________________________________    Esters of nodusmicin                                                                                          Agar Diffusion                                                                1 mg./ml. MIC mcg./ml..sup.3                                             Exact                                                                               S.aureus                                                                          S.lutea                                                                            S.aureus                                                                           S.aureus                                                                           S.aureus                                                                           S.pyrogenes          U-No.                                                                             Name       Molecular Weight                                                                          Mass UC 80                                                                              UC-130                                                                             UC-76.sup.1                                                                        UC-570.sup.1                                                                       UC-746.sup.2                                                                       UC-152               __________________________________________________________________________        18-O--benzoyl-                                                                           C.sub.30 H.sub.38 O.sub.8                                                            526.2566                                                                           526.2591                                                                           --   24        insoluble                          9-O--benzoyl-                                                                            C.sub.30 H.sub.38 O.sub.8                                                            526.2566                                                                           526.2581                                                                           --   30        insoluble                      60,906                                                                            9-O--Nicotinoyl-                                                                         C.sub.29 H.sub.37 O.sub.8 N                                                          527.2519                                                                           527.2504                                                                           NZ   32   250  250  250  2500                                                 (no zone)                                     60,898                                                                            9-O--Furoyl-                                                                             C.sub.28 H.sub.36 O.sub.9                                                            516.2359                                                                           516.2372                                                                           30   40   7.8  7.8  7.8  >250                 60,905                                                                            11-O--Furoyl-                                                                            C.sub.28 H.sub.36 O.sub.9                                                            516.2359                                                                           516.2366                                                                           NZ   17   500  500  500  >500                 60,907                                                                            18-O--Pyrrole-                                                                           C.sub.28 H.sub.37 O.sub.8 N                                                          515.2519                                                                           515.2508                                                                           27   33   7.8  3.9  15.6 >250                     2-carbonyl                                                                60,908                                                                            9,18-O--Dipyrrole-                                                                       C.sub.33 H.sub.40 O.sub.9 N.sub.2                                                     608.2734                                                                          608.2718                                                                           24   29        insoluble                          2-carbonyl-                                                               59,760                                                                            9-O--Pyrrole-                                                                            --          --   37   44   0.0625                                                                             0.0312                                                                             0.0312                                                                             >125                     2-carbonyl                                                                60,909                                                                            9-O--Picolinoyl-                                                                         C.sub.29 H.sub.37 O.sub.8 N                                                          527.2519                                                                           527.2499                                                                           NZ   31   >250 >250 >250 >250                  -- 9,11-O-Dipicoli-                                                                         C.sub.35 H.sub.38 O.sub.8 N.sub.2                                                    614.2627                                                                           614.2605                                                                           NZ   NZ    --   --   --   --                      noyl-                                                                     60,910                                                                            9-O--Thiophene-                                                                          C.sub.28 H.sub.36 O.sub.8 S                                                          532.2131                                                                           532.2127                                                                           35   40   0.5  0.25 0.5  125                      3-carbonyl-                                                               60,925                                                                            9-O--Isonicotin-                                                                         C.sub.29 H.sub.37 O.sub.8 N                                                          527.2519                                                                           527.2509                                                                           NZ   38   250  250  250  >250                     oyl                                                                       60,933                                                                            9-O--L-Pyrolyl-                                                                          C.sub.28 H.sub.41 O.sub.8 N                                                          519.2832                                                                           519.2816                                                                           16   38   31.2 62.5 62.5 >250                 60,988                                                                            9-O--N--Methyl-                                                                          C.sub.29 H.sub.39 O.sub.8 N                                                          529.2675                                                                           529.2660                                                                           NZ   24   250  >250 250  125                      pyrrole-2-                                                                    carbonyl-                                                                 60,989                                                                            9-O--Thiophene-2-                                                                        C.sub.28 H.sub.36 O.sub.8 S                                                          532.2131                                                                           532.2105                                                                           27   41   3.9  3.9  3.9  125                      carbonyl-                                                                 60,990                                                                            9-O--5-Nitrofur-                                                                         C.sub.28 H.sub.35 O.sub. 11 N                                                        561  weak NZ   33   31.2 31.2 62.5 125                      oyl                                                                       61,265                                                                            9-O--5-Methyl-                                                                           C.sub.29 H.sub.39 O.sub.8 N                                                          529.2676                                                                           529.2665                                                                           20   30   31.2 31.2 31.2 125                      pyrrole-2-                                                                    carbonyl                                                                  61,264                                                                            9-O--Pyrrazine-                                                                          C.sub.28 H.sub.36 O.sub.8 N.sub.2                                                    528       NZ   27   >125 >125 >125 >125                     2-carbonyl                                                                61,273                                                                            9-O--Indole-2-                                                                           C.sub.32 H.sub.39 O.sub.8 N                                                          565.2676                                                                           565.2690                                                                           NZ   22        insoluble                          carbonyl-                                                                 61,427                                                                            9-O--5-Nitro-                                                                            C.sub.28 H.sub.36 O.sub.10 N.sub.2                                                   560.2370                                                                           560.2414                                                                           NZ   32   125  250  125  250                      pyrrole-2-                                                                    carbonyl-                                                                 61,462                                                                            9-O--4-Nitro-                                                                            C.sub.28 H.sub.36 O.sub.10 N.sub.2                                                   560.2370                                                                           560.2387                                                                           20   36   15.6 31.2 31.2 125                      pyrrole-2-                                                                    carbonyl-                                                                 61,461                                                                            9-O--3-Furoyl-                                                                           C.sub.28 H.sub.30 O.sub.9                                                            516.2359                                                                           516.2376                                                                           35   41   0.50 0.25 0.50 2.50                 61,463                                                                            9-O--5-Bromo-                                                                            C.sub.28 H.sub.35 O.sub.9 Br                                                         594.1464                                                                           594.1492                                                                            0   35        insoluble                          furoyl-                                                                   59,761                          NZ   40   125  250  250  500                  59,760                          38   44   0.125                                                                              0.175                                                                              0.125                                                                              62.5                 __________________________________________________________________________     .sup.1 Sensitive strain                                                       .sup.2 Resistant to tetracycline                                              .sup.3 Minimum Inhibitory Concentration                                  

We claim:
 1. A compound of the formula ##STR3## wherein R is H in nomore than two positions at the same time, a blocking group in at leastone position, said blocking group selected from the group consisting oftrisubstituted silyl ethers, substituted and unsubstitutedtetrahydropyranyl ethers, β,β,β-trichloroethyl ether, and carbonateesters, or a radical of the formula ##STR4## in no more than twopositions at the same time, wherein X is selected from the groupconsisting of NH, S and O; R₁, R₂ and R₃ are the same or different andare selected from the group consisting of H, OH, halogen, NO₂, alkyl of1 to 8 carbons, inclusive, NH₂, NR₄ R₅, wherein R₄ and R₅ can beselected from the group consisting of H, OH, and alkyl and substitutedalkyl, wherein the alkyl is from 1 to 8 carbon atoms, inclusive, and thesubstituent on substituted alkyl can be OH, halogen, and SH,; O- andS-alkyl, wherein alkyl is from 1 to 8 carbon atoms, inclusive; O acyl,and N acyl, wherein the acyl radical is a hydrocarbon carboxylic acidacyl of from 2 to 18 carbon atoms, inclusive; or a halo-, nitro-,hydroxy-, amino-, cyano-, thiocyano-, or loweralkoxy-substitutedhydrocarbon acyl radical of from 2 to 18 carbon atoms, inclusive,excluding wherein X is N, R₁ = R₂ =R₃ and H, and ##STR5## is on the 2position of the molecule.
 2. A compound of the formula, according toclaim 1 ##STR6## wherein R is a radical of the formula ##STR7## whereinX is selected from the group consisting of NH, S and O; R₁, R₂ and R₃are the same or different and are selected from the group consisting ofH, OH, halogen, NO₂, alkyl of 1 to 8 carbons, inclusive, NH₂, NR₄ R₅,wherein R₄ and R₅ can be selected from the group consisting of H, OH,and alkyl and substituted alkyl, wherein the alkyl is from 1 to 8 carbonatoms, inclusive, and the substituent on substituted alkyl can be OH,halogen, SH-; O- and S-alkyl, wherein alkyl is from 1 to 8 carbon atoms,inclusive; O acyl, and N acyl, wherein the acyl radical is a hydrocarboncarboxylic acid acyl of from 2 to 18 carbon atoms, inclusive; or ahalo-, nitro-, hydroxy-, amino-, cyano-, thiocyano-, orloweralkoxy-substituted hydrocarbon acyl radical of from 2 to 18 carbonatoms, inclusive, excluding wherein X is N, R₁ =R₂ =R₃ and are H, and##STR8## is on the 2 position of the molecule.
 3. A compound of theformula, according to claim 1 ##STR9## wherein R is a radical of theformula ##STR10## wherein X is selected from the group consisting of NH,S and O; R₁, R₂ and R₃ are the same or different and are selected fromthe group consisting of H, OH, halogen, NO₂, alkyl of 1 to 8 carbons,inclusive, NH₂, NR₄ R₅, wherein R₄ and R₅ can be selected from the groupconsisting of H, OH, and alkyl and substituted alkyl, wherein the alkylis from 1 to 8 carbon atoms, inclusive, and the substituent onsubstituted alkyl can be OH, halogen, SH; O- and S-alkyl, wherein alkylis from 1 to 8 carbon atoms, inclusive; O acyl, and N acyl, wherein theacyl radical is a hydrocarbon carboxylic acid acyl of from 2 to 18carbon atoms, inclusive; or a halo-, nitro-, hydroxy-, amino-, cyano-,thiocyano-, or loweralkoxy-substituted hydrocarbon acyl radical of from2 to 18 carbon atoms, inclusive, excluding wherein X is N, R₁ =R₂ =R₃and are H, and ##STR11## is on the 2 position of the molecule.
 4. Acompound of the formula, according to claim 1 ##STR12## wherein R is aradical of the formula ##STR13## wherein X is selected from the groupconsisting of NH, S and O; R₁, R₂ and R₃ are the same or different andare selected from the group consisting of H, OH, halogen, NO₂, alkyl of1 to 8 carbons, inclusive, NH₂, NR₄ R₅, wherein R₄ and R₅ can beselected from the group consisting of H, OH, and alkyl and substitutedalkyl, wherein the alkyl is from 1 to 8 carbon atoms, inclusive, and thesubstituent on substituted alkyl can be OH, halogen, SH; O- and S-alkyl,wherein alkyl is from 1 to 8 carbon atoms, inclusive; O acyl, and Nacyl, wherein the acyl radical is a hydrocarbon carboxylic acid acyl offrom 2 to 18 carbon atoms, inclusive; or a halo-, nitro-, hydroxy-,amino-, cyano-, thiocyano-, or loweralkoxy-substituted hydrocarbon acylradical of from 2 to 18 carbon atoms, inclusive, excluding wherein X isN, R₁ =R₂ =R₃ and are H, and ##STR14## is on the 2 position of themolecule.
 5. 9-O-Thiophene-3-carbonyl-18-O-butyldimethylsilyl ester ofantibiotic nodusmicin. 6.9,11-O-Dithiophene-3-carbonyl-18-O-butyldimethylsilyl ester ofantibiotic nodusmicin.
 7. 9-O-2-Furoyl-18-O-butyldimethylsilyl ester ofantibiotic nodusmicin.
 8. 11-O-2-Furoyl-18-O-butyldimethylsilyl ester ofantibiotic nodusmicin.
 9. 9,11-O-difuroyl-18-O-butyldimethylsilyl esterof antibiotic nodusmicin. 10.9-O-Pyrrole-2-carbonyl-18-O-butyldimethylsilyl ester of antibioticnodusmicin.
 11. 9-O-N-Methylpyrrole-2-carbonyl-18-O-butyldimethylsilylester of antibiotic nodusmicin. 12.9-O-5-Nitrofuroyl-18-O-butyldimethylsilyl ester of antibioticnodusmicin.
 13. 9-O-Thiophene-2-carbonyl-18-O-butyldimethylsilyl esterof antibiotic nodusmicin. 14.9-O-5-Methylpyrrole-2-carbonyl-18-O-butyldimethylsilyl ester ofantibiotic nodusmicin. 15.9-O-5-Nitropyrrole-2-carbonyl-18-O-butyldimethylsilyl ester ofantibiotic nodusmicin. 16.11-O-5-Nitropyrrole-2-carbonyl-18-O-butyldimethylsilyl ester ofantibiotic nodusmicin. 17.9-O-4-Nitropyrrole-2-carbonyl-18-O-butyldimethylsilyl ester ofantibiotic nodusmicin.
 18. 9-O-3-Furoyl-18-O-butyldimethylsilyl ester ofantibiotic nodusmicin.
 19. 9,11-O-Di-3-furoyl-18-O-butyldimethylsilylester of antibiotic nodusmicin. 20.9-O-5-Bromofuroyl-18-O-butyldimethylsilyl ester of antibioticnodusmicin.
 21. 9,11-O-Di-5-bromofuroyl-18-O-butyldimethylsilyl ester ofantibiotic nodusmicin.
 22. 9-O-Furoyl ester of antibiotic nodusmicin.23. 11-O-Furoyl ester of antibiotic nodusmicin. 24.18-O-Pyrrole-2-carbonyl ester of antibiotic nodusmicin. 25.9,18-O-Dipyrrole-2-carbonyl ester of antibiotic nodusmicin. 26.9,O-Thiophene-3-carbonyl ester of antibiotic nodusmicin. 27.9-O-N-Methyl-pyrrole-2-carbonyl ester of antibiotic nodusmicin. 28.9-O-Thiophene-2-carbonyl ester of antibiotic nodusmicin. 29.9-O-5-Nitrofuroyl ester of antibiotic nodusmicin. 30.9-O-5-Methylpyrrole-2-carbonyl ester of antibiotic nodusmicin. 31.9-O-5-Nitropyrrole-2-carbonyl ester of antibiotic nodusmicin. 32.9-O-4-Nitropyrrole-2-carbonyl ester of antibiotic nodusmicin. 33.9-O-3-Furoyl ester of antibiotic nodusmicin.
 34. 9-O-5-Bromofuroyl esterof antibiotic nodusmicin.